package com.nowcoder.community.util;

import org.apache.commons.lang3.CharUtils;
import org.apache.commons.lang3.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;
import org.springframework.web.bind.annotation.PathVariable;

import javax.annotation.PostConstruct;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.HashMap;
import java.util.Map;

@Component
public class SensitiveFilter {
    private static final Logger logger= LoggerFactory.getLogger(SensitiveFilter.class);
    private static final String REPLACEMENT="***";
    //根节点
    private TrieNode rootNode=new TrieNode();

    @PostConstruct
    public void init(){
        try(InputStream is = this.getClass().getClassLoader().getResourceAsStream("sensitive.txt");
            BufferedReader reader=new BufferedReader(new InputStreamReader(is));)
        {
            String keyword;
            while((keyword=reader.readLine())!=null){
                //添加到前缀树
                this.addKeyword(keyword);
            }
        }catch (IOException e){
            logger.error("加载敏感词失败:"+e.getMessage());
        }

        }

            //将一个敏感词添加到前缀树中
        private void addKeyword(String keyword){
        TrieNode tempNode=rootNode;
        for(int i=0;i<keyword.length();i++){
            char c=keyword.charAt(i);
            TrieNode subNode = tempNode.getSubNode(c);
            if(subNode==null){
                //初始化子节点
                subNode =new TrieNode();
                tempNode.addSubNode(c,subNode);
            }
            //指向子节点，进入下一轮循环
            tempNode=subNode;
            //设置结束标识
            if(i==keyword.length()-1){
                tempNode.setKeywordEnd(true);
            }
        }
    }

    /**
     * 过滤敏感词
     * @param text 待过滤文本
     * @return 过滤后文本
     */
    public String filter(String text){
        if(StringUtils.isBlank(text)){
            return null;
        }
        //指针1
        TrieNode tempNode=rootNode;
        //指针2
        int begin =0;
        //指针3
        int position=0;
        //结果
        StringBuilder sb = new StringBuilder();
        while(position<text.length()){
            char c=text.charAt(position);
           //跳过符号
            if(isSymbol(c)){
                //若指针1属于根节点，将此符号计入结果，让指针2向下走一步
                if(tempNode==rootNode){
                    sb.append(c);
                    begin++;

                }
                //无论符号在开头或中间，指针3都向下走一步

                position++;
                continue;
            }
            //检查下级节点
            tempNode=tempNode.getSubNode(c);
            if(tempNode==null){
                //以begin为开头的字符串不是敏感词
                sb.append(text.charAt(begin));
                //进入下一个位置
                position=++begin;
                //重新指向根节点
                tempNode=rootNode;
            }else if(tempNode.isKeywordEnd()){
                //发现敏感词，将begin-position字符串替换掉
                sb.append(REPLACEMENT);
                //进入下一个位置
                begin=++position;
                //重新指向根节点
                tempNode=rootNode;

            }else{
                //检查下一个字符
                position++;
            }
        }
        //将最后一批字符计入结尾
        sb.append(text.substring(begin));

        return sb.toString();
    }
    //判断是否为符号
    private boolean isSymbol(Character c){
        return !CharUtils.isAsciiAlphanumeric(c)&&(c<0x2E80||c>0X9FFF);
    }
    //前缀树
    private class TrieNode{
        //关键词结束标识
        private boolean isKeywordEnd=false;

        //子节点(key是下级字符，value是下级节点)
        private Map<Character,TrieNode> subNodes=new HashMap<>();


        public boolean isKeywordEnd() {
            return isKeywordEnd;
        }

        public void setKeywordEnd(boolean keywordEnd) {
            isKeywordEnd = keywordEnd;
        }
        //添加子节点
        public void addSubNode(Character c,TrieNode node){
            subNodes.put(c,node);
        }
        //获取子节点
        public TrieNode getSubNode(Character c){
            return subNodes.get(c);

        }
    }
}
